High Internal Loads Research Articles

Overview of Recent Three-Dimensional, Small-Scale, Mini-Pipe Testing of Carbon Steel Well Tubulars with Internal Pressure, Axial Load, and Internal/External Hydrogen Sulfide Exposure

Abstract Mini-pipe testing has been used to expose miniature low-alloy carbon steel pipes to one-sided and two-sided hydrogen sulfide (H2S) combined with high internal pressures (20,000+ psi) and axial loads. This paper explains the types of tests that have been performed and the results that have been observed. One-sided vs two-sided H2S exposure combined with stress gradients across the pipe wall is shown to lead to differences in pipe performance. Test results indicate a substantial increase in pipe material performance when one-sided H2S exposure is taken into account compared with two-sided H2S exposure. Tests of prenotched mini-pipes are introduced, which indicate that a fracture mechanics formula using KISSC from the double-cantilever beam (DCB) test is nonconservative and overpredicts the pipe failure pressure due to sulfide stress cracking. Use of the limiting value, KISSC-Limit, is shown to improve the prediction of pipe cracking failure significantly, making it almost conservative. Use of KISSC...

Concentration of plastic strains in steel liners due to concrete cracks in the containment wall

A substantial part of nuclear containments in US and Europe are designed with an outer bearing concrete structure and an inner sealing consisting of a tight-welded steel liner. The liner constitutes the ultimate leak-barrier, which prevents leakage at high internal pressure loads. The purpose of this paper is to show which influence a through-wall concrete crack may have on the strain level in the liner. A non-linear bar model is used to evaluate the liner behavior. It is shown that the effect from friction between the concrete and liner could be significant and cause high concentration of plastic strain. The influence of friction on the liner is verified by an experimental program presented in this paper. One of the conclusions is that concentrations of strain due to friction increase with decreasing liner thickness. This is important to consider when results from scale tests are interpreted. Scale models, which have thinner liners, could get significantly higher liner strain than the actual full-scale containment.

Nutrient accumulation and nutrient retention in coastal waters – 30 years investigation in the Darss‐Zingst Bodden chain

AbstractCoastal waters are transitional zones between limnic waters and marine systems. The anthropogenic impact on these water bodies is high and a rapid change of trophic level was observed within the last 50 years. In the Darss‐Zingst Bodden chain (southern Baltic Sea – Mecklenburg‐West Pomerania, Germany), the change in trophic state during the last thirty years can be reconstructed by long‐term monitoring of chemical, hydrographical and biological parameters with an up to daily resolution. Until the 1980s, increased input of the anthropogenic nutrient load from the catchment area has been documented. However, with the implementation of the HELCOM recommendations the input of phosphorus and nitrogen was reduced in the 1990s. In contrast to the reduction of nutrient inputs, a decrease in nutrient concentrations and primary production could not be observed. The reasons are a high internal nutrient load and the release of nutrients out of the sediments. Numerous research projects allowed the description and quantification of these processes. Today, the internal phosphorus pool exceeds the external phosphorus load several fold. These results are the scientific basis for the development of restoration strategies of coastal waters. The development of suitable management plans is necessary for the implementation of the EU Water Framework Directive to guarantee a good ecological state by 2015. The long time acquisition of monitoring data and voluminous complementary specific research projects was enabled by the local field research conditions of the Biological Station of the University of Rostock in Zingst.

Passive and Low Energy Cooling of Office Buildings

In this work, the cooling performance of night ventilation systems and different earth heat exchange technologies were experimentally analysed in three office buildings in Southern Germany. One of the first passive energy standard office buildings in Europe was extensively monitored over a three year period to analyse the summer performance of a highly insulated and well shaded building in which night cooling ventilation was based on stack effect and cross ventilation. This was combined with a mechanical ventilation system incorporating a ground coupled heat exchanger to supply daytime fresh air.For comparison, an energy analysis was made of a mechanically driven exhaust air night ventilation system and a supply and exhaust air system in the other two buildings. The first of these was a passively cooled refurbished building in Tübingen which utilises mechanical night ventilation to effectively discharge ceilings with phase change material. In addition, fresh air cooling is achieved using a horizontal brine-earth heat exchanger. The second comparison building was a low energy office building in Freiburg which uses water based ground coupled heat exchangers for fresh air cooling and an exhaust air ventilation system for night cooling.During a typical German summer, in which the number of hours that the ambient air temperature exceeds 25°C is less than 160, the passively ventilated building performed excellently, even with relatively high internal heat loads of 200 to 400 Wh.m−2.day−1. However, when the ambient air temperature was significantly higher, such as in the summer of 2003 (i.e. 3 K higher than the average summer temperature), nearly 10% of all office hours recorded room air temperatures above 26 °C. In the case of the two buildings that were night cooled by mechanical ventilation, cooling performance was limited by the rather low air exchange rate of 2 h−1. This resulted in overnight room temperature reductions of just 2–3 K during hot summer nights. Also the coefficient of performance (COP) was relatively low for this approach at between 4 to 6.All the earth heat exchangers showed excellent energy performances with COP's between 20 and 50. However, due to the limited fresh air volume flow in such buildings, the earth heat exchanger only removed a small part of the total load.

Glenohumeral joint loading in tetraplegia during weight relief lifting: A simulation study

The incidence of shoulder complaints in wheelchair users is high and the etiology is poorly understood. The goal of this study was to examine the effect of lesion level and isolated triceps muscle paresis on the internal load on the shoulder by simulation. Kinematic and kinetic profiles from four able-bodied subjects and four subjects with tetraplegia were used as input for an inverse dynamics biomechanical model. The model was modified to simulate lesion level and triceps muscle paresis. The simulations resulted in a significantly higher (+56%) glenohumeral contact force (P=0.037) for tetraplegic profiles than for able-bodied profiles. The model modifications to simulate lesion level only had a minor effect (+7%) on the calculated glenohumeral contact force. More simulations were successful at lower triceps force levels for tetraplegic profiles compared to able-bodied profiles (P=0.012). The muscle forces at the simulated T1 lesion were not significantly higher in tetraplegic profiles compared to able-bodied profiles. The glenohumeral contact force for the tetraplegic profiles is mainly higher due to different task performance. Model modifications only have a minor effect on the calculated glenohumeral contact force. For able-bodied profiles the triceps force seems to be an important factor. The high internal load at the shoulder recommends new techniques of weight relief lifting and proper training of the arm-shoulder muscles in rehabilitation.

Dietary Phosphorus Modifications in Practical Feeds Do Not Affect Waterborne Phosphorus Concentrations and Phytoplankton Abundance in Channel Catfish Ponds

AbstractWe measured concentrations of soluble reactive phosphorus, total phosphorus, and chlorophyll a in 0.04‐ha ponds containing channel catfish Ictalurus punctatus during three feeding trials to evaluate the effect of dietary phosphorus modifications on water quality and the potential discharge of phosphorus and organic matter in pond effluents. In experiment 1, a basal diet with 0.20% available phosphorus was compared with diets supplemented with 0.5% or 1.0% dicalcium phosphate to provide 0.27% or 0.35% available phosphorus. In experiment 2, fish were fed diets supplemented with either dicalcium phosphate or defluorinated rock phosphate to contain 0.40% available phosphorus. In experiment 3, fish were fed one of three diets containing 250 or 500 phytase units of phytase per kilogram (0.27% available phosphorus) or 0.75% dicalcium phosphate (0.39% available phosphorus). Husbandry practices in all three experiments were typical of commercial culture conditions. Quantitative and qualitative modifications of dietary phosphorus did not affect waterborne phosphorus concentrations or phytoplankton abundance and, therefore, will not reduce phosphorus or organic matter mass loading in pond effluents. Lack of effectiveness results from high baseline nutrient loading from phosphorus contained in practical feed ingredients combined with high internal phosphorus loading (recycling) within ponds. These factors overwhelm any effect of small changes in external phosphorus loading associated with diet modification. Therefore, the source and level of dietary phosphorus in channel catfish feeds should be based on nutritional and economic considerations rather than potential environmental impact.

Vitellogenin content in European eel ( Anguilla anguilla) in Flanders, Belgium

As part of a large-scale monitoring program of bioaccumulating contaminants in the European eel ( Anguilla anguilla) in Flanders (Belgium), we investigated potential effects of xenoestrogens in these fish. The present paper describes the results of the plasma vitellogenin (VTG) content, measured in 142 eels sampled at 20 different locations, in relation to the internal pollution levels. To validate the blood VTG assays, a small number of eels ( n=8) was exposed to 10 μg ethinylestradiol/l (EE2) for 9 days. In this experiment, VTG was detected as a protein with a molecular weight of 214 kDa and confirmed by Western blotting. Compared with the solvent controls, significantly higher concentrations of VTG were measured in EE2 exposed eel. However, the VTG content was relatively low compared with other fish species exposed to high concentrations of estrogens. The plasma VTG content of eels from the field study was very low, despite a very high internal load of endocrine disrupters. These results, together with previously published studies, suggest that immature yellow European eel might not be the best sentinel species to study the effects of estrogenic compounds on VTG levels of wild fish populations.

Effects of destratification and fish removal on the genus Microcystis in a shallow hypertrophic lake

The boreal Lake Tuusulanjarvi is hypertrophic due to high diffuse and internal loading maintained by hypolimnetic oxygen depletion and a high density of cyprinids. The phytoplankton community, especially of cyanophyta (cyanobacteria, cyanoprokaryota) in the lake is highly diverse, and Lake Tuusulanjarvi has been characterized as a botanical garden of the genus Microcystis. The abundant cyanophyta, producing nuisance algal blooms, has generated a need for intensive restoration activities. Since the autumn of 1997, effective destratification and biomanipulation have decreased the internal loading. As a result of lower nutrient levels the phytoplankton biomass, especially of cyanophyta, has decreased and transparency has increased. The biomass of cyanophyta was lowest in summers after the highest removal of fish biomass. During the study period 69 taxa of cyanophyta were identified, High nutrient concentrations clearly explained the occurrence of some morphotypes of Microcystis. M. wesenbergii, M. aeruginosa and M. viridis, which are embedded in a specific kind of mucilaginous sheath, were considered as morphotypes occurring during different phases of stratification. M. wesenbergii and M. viridis were the most resistant species to biomanipulation and destratification.

Role of sediment and internal loading of phosphorus in shallow lakes

The sediment plays an important role in the overall nutrient dynamics of shallow lakes. In lakes where the external loading has been reduced, internal phosphorus loading may prevent improvements in lake water quality. At high internal loading, particularly summer concentrations rise, and phosphorus retention can be negative during most of the summer. Internal P loading originates from a pool accumulated in the sediment at high external loading, and significant amounts of phosphorus in lake sediments may be bound to redox-sensitive iron compounds or fixed in more or less labile organic forms. These forms are potentially mobile and may eventually be released to the lake water. Many factors are involved in the release of phosphorus. Particularly the redox sensitive mobilization from the anoxic zone a few millimetres or centimetres below the sediment surface and microbial processes are considered important, but the phosphorus release mechanisms are to a certain extent lake specific. The importance of internal phosphorus loading is highly influenced by the biological structure in the pelagic, and lakes shifting from a turbid to a clearwater state as a result of, for example, biomanipulation may have improved retention considerably. However, internal loading may increase again if the turbid state returns. The recovery period following a phosphorus loading reduction depends on the loading history and the accumulation of phosphorus in the sediment, but in some lakes a negative phosphorus retention continues for decades. Phosphorus can be released from sediment depths as low as 20 cm. The internal loading can be reduced significantly by various restoration methods, such as removal of phosphorus-rich surface layers or by the addition of iron or alum to increase the sediment's sorption capacity.

3- and 4-Contact Point Spindle Bearings – a new Approach for High Speed Spindle Systems

One important demand on spindle systems in modem machine tools is to realise higher rotational speeds in order to increase the machining efficiency. In conventional spindle bearings the contact angles on inner and outer ring deviate extremely from one another with rising rotational speeds due to centrifugal forces. Axial shift of trie inner ring (elastic mounted bearing) and increasing normal forces in the contact zones on the outer ring are typical consequences leading to high internal bearing loads and a reduced life span. Based on these problems bearings with a new inner geometry are studied. Instead of two contact zones these bearings have three or four contact zones to ensure constant contact angles and reduced normal forces on the outer ring. In this paper analytic operation studies and first experimental tests are presented.

A new parallel wrist using only revolute pairs: the 3-RUU wrist

Only one parallel wrist with three equal legs containing just revolute pairs has been already presented in the literature. This parallel wrist is overconstrained, i.e., it involves three degrees of freedom required to orientate the end effector by using repetitions of constraints. The overconstrained mechanisms have the drawback of jamming or undergoing high internal loads when geometric errors occur. This paper presents a new parallel wrist, named 3-RUU wrist. The 3-RUU wrist is not overconstrained. It has three equal legs just involving revolute pairs and actuators adjacent to the frame and uses an architecture (3-RUU) already employed to obtain manipulators that make the end effector translate. The 3-RUU wrist kinematic analysis is addressed. This analysis shows that the new parallel wrist can reach singular configurations (translation singularities) in which the spherical constraint between end effector and frame fails. The singularity condition that makes finding all the 3-RUU wrist singular configurations possible is written in explicit form and geometrically interpreted.

A Management Alternative for Lake Apopka

ABSTRACT We examine the idea that whenever high levels of planktonic algae impair a lake, nutrient control is the first step to be taken regardless of what other management actions might be contemplated. Our example is Lake Apopka, a 12,500 ha, shallow (1.7 m), polymictic lake in central Florida. Prior to 1947, the lake was dominated by macrophytes, was reputed to have clear waters, and had a national reputation for its largemouth bass fishery. Following a hurricane in 1947, the lake switched to a turbid, algal state and the bass fishery is all but gone. For over 30 years, it was either implied or stated directly that nutrient enrichment from anthropogenic activities, especially farms along the north shore, was to blame for this change and the lack of macrophyte recovery. The current management plan is to remove the farm nutrient supply by purchasing the farms under the theory that this will lower the total phosphorus concentration in the water and thus restore the lake. We have developed the most probable phosphorus budgets for the lake based on the studies of others and have determined that a fluid mud layer that is frequently resuspended by the wind will lead to high internal loading and slow the drop in phosphorus concentration. The equilibrium phosphorus concentration will lie between 52 and 88 mg·m−3, so the lake will remain in its eutrophic state. We propose an alternative management plan using artificial reefs that will focus on restoring the largemouth bass fishery in the immediate future. This idea is attractive because bass fishing was the dominant use of this lake in the past, it can be accomplished without waiting for a change in trophic state, and it can produce results in a relatively short period of time.

Integrated sidestream treatment for enhanced enlargement of sewage plants

The filtrates or centrates from dewatering of digested sludges cause high internal nitrogen loads on sewage treatment plants. Especially at poor inflow C:N ratios separate treatment of these sludge liquors can significantly relieve the biological treatment stage. We developed a new process for a biological sidestream treatment with primary sludge as the carbon source for denitrification. The process has beeen tested in laboratory-scale tests and by computer simulations. The stability of the process is being investigated in a full-scale application under practical conditions.

Effects of Phosphorus Reduction on Water Quality: Comparison of Alum-Treated and Untreated Portions of a Hypereutrophic Lake

ABSTRACT The effects of a reduction in total phosphorus concentration on the water quality and plankton community structure in a 86-ha hypereutrophic sandpit lake with high internal phosphorus loading were assessed by dosing an isolated 4.6-ha section of the lake with 34,065 L (dose = 10 mg Al·L−1) of liquid aluminum sulfate (alum). During the three summers following treatment, hypolimnetic total dissolved phosphorus, epilimnetic total phosphorus, and eplimnetic total nitrogen were decreased by 97%, 74%, and 36%, respectively, in the treated section. Secchi depth was 134% greater in the treated area. Alum treatment also increased the volume of usable fish habitat by 22%, as the depth of the 3.0-mg/l dissolved oxygen isocline was 52% deeper in the treated portion than in the untreated portion. Total phytoplankton biovolume decreased by 40% and chl a concentration by 65% in the treated area. Although cyanophytes continued to dominate in die treated area, there was a shift in relative abundance from cyanophytes to bacillariophytes and chlorophytes, especially during the second summer after treatment. By the second post-treatment summer, daphnid biomass increased substantially and there was a subtle shift in relative abundance from copepods to daphnids. Overall, alum was extremely effective in controlling sediment phosphorus release rates and lowering water column phosphorus concentrations and thus improving water clarity, reducing phytoplankton biomass, shifting phytoplankton species composition from cyanophyte dominance toward bacillariophytes and chlorophytes, increasing daphnid biomass, and increasing usable fish habitat.

Evaporative Air Conditioning In a Manufacturing Facility

A case study evaluates the economics of installing a staged evaporative cooling system in a factory in the southeastern USA. The effective temperature at the plant floor is predicted for each working hour from typical meteorological year data. The analysis accounts for internal loads and moisture evaporated by the manufacturing process. Worker productivity is estimated from the effective temperature. Several building loads and evaporative cooling system designs are considered. The results show that evaporative air conditioning can improve worker productivity and profit margins in manufacturing facilities that have high internal loads, high ventilation requirements, or other plant-specific conditions that would make conventional air conditioning uneconomical.

Cascading Trophic Interactions from Fish to Bacteria and Nutrients after Reduced Sewage Loading: An 18-Year Study of a Shallow Hypertrophic Lake

The effects of major reductions in organic matter, total phosphorus (TP), and total nitrogen (TN) loading on the chemical environment, trophic struc- ture, and dynamics of the hypertrophic, shallow Lake Sobygard were followed for 18 years. After the reduction in organic matter loading in 1976, the lake initially shifted from a summer clear-water state, most likely reflecting high grazing pressure by large Daphnia species, to a turbid state with ex- tremely high summer mean chlorophyll a (up to 1400 µg L 21 ), high pH (up to 10.2), and low zooplankton grazing. Subsequently, a more variable state with periodically high grazing rates on phyto- plankton and bacteria was established. Changes in zooplankton abundance and grazing could be attrib- uted to variations in cyprinid abundance due to a fish kill (probably as a consequence of oxygen depletion) and pH-induced variations in fish recruit- ment and fry survival. The results suggest strong cascading effects of fish on the abundance and size of zooplankton and phytoplankton and on phyto- plankton production. A comparatively weak cascad- ing effect on ciliates and bacterioplankton is sug- gested. Due to high internal loading, only minor changes were observed in lake-water TP after a reduction in external TP loading of approximately 80% in 1982; net retention of TP was still negative 13 years after the loading reduction, despite a short hydraulic retention time of a few weeks. TN, how- ever, decreased proportionally to the TN-loading reduction in 1987, suggesting a fast N equilibration. Only minor improvement in the environmental state of the lake has been observed. We suggest that another decade will be required before the lake is in equilibrium with present external P loading.

Effects of hypolimnetic oxygenation on water quality in Amisk Lake, Alberta, a deep, eutrophic lake with high internal phosphorus loading rates

Year-round injection of pure oxygen into the hypolimnion of one of two basins in Amisk Lake during 1988-1993 changed dissolved oxygen (DO) and nutrient concentrations in both lake basins without eliminating thermal stratification. Changes were greatest in the treated basin and during 1990-1993, when an upgraded injection system operated; injection rates of <<= 1.3 t · day-1increased mean summer hypolimnetic DO concentrations from 1.0 (1980-1987) to 4.6 mg ·L-1(1990-1993). Summer hypolimnetic DO depletion rates nearly doubled relative to the pretreatment period. Mean summer hypolimnetic total phosphorus (TP) concentrations decreased from 123 to 56 µg · L-1, despite low iron to phosphorus ratios near the sediments. Similarly, mean hypolimnetic ammonium concentrations declined from 120 to 42 µg ·L-1. Epilimnetic TP and chlorophyll a concentrations decreased to 87 and 45%, respectively, of pretreatment summer means. Oxygen consumption rates in the treated basin were lower in winter than in summer; injection rates of <<= 0.8 t ·d-1increased mean winter deepwater DO concentrations from 2.5 to 7.2 mg ·L-1. In winter, mean deepwater TP concentrations decreased from 96 to 51 µg ·L-1. Oxygenation enhanced deepwater circulation in the treated basin in summer and winter. No changes were seen in two other reference basins during the study period. The hypolimnetic oxygen injection technology developed at Amisk Lake can be a cost-effective management tool for lakes with high hypolimnetic oxygen depletion rates related to high internal nutrient loading rates.

Coping with Water Quality Problems due to Hypolimnetic Anoxia in Central Ontario Lakes

Abstract Many lakes experience oxygen depletion in their hypolimnia during summer or winter stratification. This study investigates the remedial actions that are available to combat the harmful effects of hypolimnetic anoxia in three types of Central Ontario lakes with different trophic states. In more eutrophic lakes, e.g., Lake Wilcox, southern Ontario, much phosphorus accumulates in the hypolimnion during anoxia and represents ca. 60% of the annual P budget. To diminish the detrimental effects of such a high internal phosphorus load, withdrawal of the hypolimnetic waters, together with damming of the surface water outflow, has been suggested. In oligo- to mesotrophic Chesley Lake, on the Niagara Escarpment, phosphorus accumulation in the hypolimnion is only slight and metals with a binding capacity for phosphorus are available. Here a hypolimnetic oxygenation has been suggested to alleviate the stress on fish and also to prevent further P release from the sediments. Lakes in the District of Muskoka are softwater lakes because of their location on the Canadian Shield. Although the geochemistry of the catchment typically renders these lakes nutrient poor and oligotrophic, long-term development on their shores has led to phosphorus accumulation in the sediments that is released under anoxic conditions in some lakes. To prevent the deterioration of the water quality in these lakes, water quality models to manage and control future development in its watersheds, as those of the district municipality, should include anoxia and internal P recycling in a quantitative manner.

Effects of hypolimnetic oxygenation on water quality in Amisk Lake, Alberta, a deep, eutrophic lake with high internal phosphorus loading rates

Effects of hypolimnetic oxygenation on water quality in Amisk Lake, Alberta, a deep, eutrophic lake with high internal phosphorus loading rates

Phosphorus release from anoxic sediments: what we know and how we can deal with it

An attempt is made to classify lakes that are especially prone to high internal phosphorus load derived from anoxic sediment surfaces. Morphometric, hydrological and geochemical characteristics of lakes with high internal P load are discussed. For example a lake with a mean depth between 5 and 12 m and an averagc flushing rate is a candidate for internal P load, especially if sediment P concentration is elevated due to eutrophication. Measures for remediation are presented like hypolimnetic withdrawal, aeration and chemical precipitation.